Rose Byrne and Oprah Winfrey star in HBO's "The Immortal Life of Henrietta Lacks," which airs on HBO on April 22. (Quantrell Colbert/HBO)

Oprah Winfrey says she lives without feeling rage, which is a nice way to go through your days but potentially limiting when you’re playing the pivotal character in a film about an emotionally scarred woman who is all but consumed by it.

Needing to get in touch with some visceral fury, Winfrey reached out to one of the students she calls “my girls” — a young woman from the South African leadership academy she famously endowed — and asked her to recount her experiences with an aunt who had beaten her. Winfrey was beaten as a child, too, but time and other sources of healing blunted the pain to the point where, as she puts it, there was no “charge” for her left.

“I asked her to tell me the story, because I didn’t have enough charge from my own beatings,” she explains. “I have to work really, really hard to pull up anger and rage. But hearing someone else talk about their beatings, I could have great empathy, great compassion, great sorrow and sadness.”

And an explosive sense of indignation, a summoning she found immensely helpful in conjuring a daughter struggling to come to grips with the fate of her long-dead mother in “The Immortal Life of Henrietta Lacks,” a movie directed and largely written by George C. Wolfe and based on the best-selling 2010 nonfiction book of that title by Rebecca Skloot. It premieres on HBO on April 22 at 8 p.m.

It’s easy to see what the attraction was for the 63-year-old Winfrey, in one of her infrequent acting forays. Her last movie role was in 2014’s “Selma,” and she appeared in her OWN 2016 drama series, “Greenleaf.” Via HBO, she took the project to Wolfe, a theater veteran, after their plans to work on a Broadway show together failed to crystallize. The film, which features Rose Byrne as Skloot and a supporting cast that includes Renée Elise Goldsberry, Reg Cathey, Courtney Vance and Leslie Uggams, tracks a reporter’s investigation into the life of Henrietta Lacks, an African American woman who died in obscurity in Baltimore in 1951, but who nevertheless became world-renowned — on a cellular level.

Scientists found that the cells cultured from her tumor samples didn’t readily die off, which meant they could reproduce again and again. As a result, these valuable cell lines, which have come to be known to research labs and biotechnology companies worldwide by Henrietta’s abbreviated name, HeLa, have been instrumental in dozens of medical breakthroughs for a number of diseases, including cancer and AIDS, and are still in use to this day.

“I see all of my work as a kind of offering,” Winfrey says in a telephone interview from her estate in Santa Barbara, Calif. “It comes from a genuine spirit of enthusiasm. I felt a genuine desire to share this story, because this is a name that people should know.”

The participation of Winfrey significantly upgrades the movie’s curiosity value. “It’s an astonishing performance,” Wolfe says. “There’s a power to her and a ferocity to her.” Winfrey takes a deep dive into rage as a consequence of portraying Henrietta’s youngest daughter, Deborah, sometimes called Dale, a woman so disordered by grief and grievance she seems to live in a limbo of distress: Although her mother’s cells have enduring purpose, Deborah can’t find any deep meaning for her own life. (Goldsberry, a Tony winner for her portrayal of Angelica Schuyler in the Broadway musical “Hamilton,” plays Henrietta in flashback sequences.) Byrne’s Skloot, sensing the inequity of a medical establishment profiting from Henrietta’s unwitting bequest but offering no compensation to her struggling descendants, persuades the erratic Deborah to team up with her to excavate material for the book. (The fight over Henrietta’s legacy has created bitter rifts among her survivors, although people involved in making the movie say the feud had no effect on it.)

Director George C. Wolfe on the set of “The Immortal Life of Henrietta Lacks.” (Quantrell Colbert/HBO)

So it’s actually the stories of two women, separated by death. By way of Deborah, the movie is about a citizen seeking redress from powerful institutions, a theme that strikes a particular nerve at this moment of deep mistrust of American government, media and other symbols of authority. The medical world, represented here by Baltimore’s august Johns Hopkins University, where Henrietta was treated and her tumor was removed, is not excused from criticism, although the movie doesn’t look for villains. Through Henrietta, the film enlarges on a positive notion, of one person contributing to the betterment of humankind in a way that transcends one’s modest circumstances, or even the knowledge the benefits have occurred.

“It is a story of economic injustice,” Wolfe insists, as he sits in the offices of a Manhattan media studio where “Henrietta Lacks’’ was edited. “But the movie is also about taking this person from abstraction and claiming this person as a tangible human being. One of the things that I really love is that in 1951, on paper, one of the least powerful people you could be is a moderate-income black woman. And yet HeLa was so powerful.”

What got to Winfrey, one of the film’s executive producers, was less the science than the search. “Her thing was not about the money,” she says of Deborah. “It was, ‘I just want to figure out who my mother was.’ ” Winfrey was encouraged in that point of view by Wolfe, she says, when he told her: “It’s the story of woman’s search for her own identity through her mother, and if she can figure out who her mother is, she can figure out who she is.”

The effort to translate Skloot’s book to the screen had gone through several false starts before Wolfe came on board, but for the author herself, the most “mind-bending” point in the process was when Winfrey signed on. Because Deborah, who died in 2009 just before the book was published, had her heart set on a chain of events that fell astonishingly into place.

“She wanted nothing more than the story to go out into the world,” Skloot says. “And she said for years she wanted Oprah to play her in the movie.” To give Winfrey even more insight into Deborah, Skloot shared with her and Wolfe hundreds of hours of tapes she and her subject recorded over the years of Skloot’s research.

Deborah Lacks Pullum had a highly developed sense of drama, as “The Immortal Life” makes abundantly clear and which, Skloot says, Winfrey managed to convey. Watching it, you do get a potent sense of Deborah’s appetite for the truth, even if that trait alienates her siblings and brings into their midst a young white reporter whose motives they don’t always understand.

“It was everything that Deborah had wanted, and she really captured her spirit,” Skloot says of Winfrey. “When I was on set and saw her in costume, Oprah ceased to be Oprah.”

Shot in rural Georgia and Baltimore — Johns Hopkins allowed its facilities to be used, Wolfe says — the movie offered roles that many actors found irresistible. Byrne, who only recently had a baby, was inclined to pass on the role, but the film revealed the relationship between a reporter and subject so freshly she couldn’t. “I’m such a snoop,” the actress confesses. “I could have missed my calling.” Cathey, a veteran of “The Wire” and “House of Cards,” who plays Deborah’s younger, damaged brother, Zakariyya, felt a bracing connection to his own losses: “I remember thinking about Mom and Dad and how I’m now an orphan.” Vance, who worked with Wolfe on the Broadway drama “Lucky Guy,” and was cast in “Henrietta Lacks” as a charlatan legal adviser who tries to bilk Henrietta’s survivors, signed up on the strength of Wolfe’s request. “He says ‘Jump,’ ” Vance says. “I say, ‘How high?’ ”

The mission to inform a wider audience was confirmed in the number of cast members who had no idea who Lacks was. For those familiar with other stories of ordinary African Americans drawn into scientific experimentation, such as the notorious study of black men with untreated syphilis in Tuskegee, Ala. throughout the mid-20th century, being unaware of Lacks’s story was nothing short of mind-boggling. “I’m a voracious reader, so I didn’t understand how I missed this,” says Uggams, cast as one of Henrietta’s surviving cousins. “And then I read the book, and I was stunned by the whole thing.”

“I’d never even heard of the HeLa line,” Goldsberry says.” Like others in the cast, though, Goldsberry came to sense a larger purpose in being able to spread the story of Henrietta’s contribution. “I felt that the story is bigger than the performances,” she adds. “Just like in ‘Hamilton,’ when it’s long overdue for the world to know about something, it becomes about serving the moment — it feels like it’s bigger than any particular group of people.”

Winfrey herself professes amazement at having Lacks’s story revealed to her only now. “And I lived in that town for eight years!” she declares, referring to her work as a reporter at a television station in Baltimore, the city where Lacks died 66 years ago. Ultimately, though, she says, she’s grateful there was another journalist to piece together this key bit of scientific history. “We owe a lot to Rebecca Skloot,” Winfrey says. “Had she not been persistent, we would not know the story.”

The Immortal Life of Henrietta Lacks premieres April 22 at 8 p.m. on HBO.